Method of preparing fluorine-containing ethane derivatives

ABSTRACT

A method of preparing fluorine-containing ethane derivatives using a catalyst mixture which comprises a metal halide and a sulfonic acid derivative is described. The method is particularly well suited for preparing CF 3  CHCl 2  (R123) from perchloroethylene and for preparing CF 3  CH 2  F (R134a) from trifluoroethylene.

This application is a division of application Ser. No. 07/683,834, filedApr. 11, 1991 U.S. Pat. No. 5,071,900.

BACKGROUND OF THE INVENTION

This invention relates to a method for preparing fluorine-containingethane derivatives corresponding to the formula F_(k) H_(n) Cl₃₋(k+n)C--CZ¹ Z² F, wherein, k ,n, Z¹ and Z² have the meanings described below.

There is an increasing need for environmentally compatible halogenatedhydrocarbons. Examples of such hydrocarbons have been found to includethe fluorinecontaining ethane derivatives which contain at least onehydrogen atom, for instance CF₃ CH₃ (R143a), CF₃ CH₂ Cl (R133a), andespecially CF₃ CHCl₂ (R123). However, the corresponding 1-fluoro or1,1-difluoro compounds are also of interest, for instance the compoundsCFCl₂ CHCl₂ or CF₂ ClCHCl₂, which are considered environmentallycompatible and which can be used as refrigerants, solvents orpropellants.

Industrially, such compounds are prepared by catalyzed halogen-fluorineexchange, particularly by chlorine-fluorine exchange, fromcorrespondingly halogenated derivatives. The halogenated startingcompounds used for this are, however, very inert with respect tohalogen-fluorine exchange. Particularly for preparing higher fluorinatedcompounds, drastic process conditions are necessary. Despite suchdrastic conditions, for instance operation in the gaseous phase, theconversions are usually low. A further drawback of known methods is thatthe catalysts used, which are often very expensive, do not have asatisfactory life.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a method ofpreparing fluorine-containing ethane derivatives which is relativelyeasy to perform industrially.

Another object of the invention is to provide a method of preparingfluorine-containing ethane derivatives which produces a high conversion.

These and other objects are achieved by providing a method of preparinga fluorine-containing ethane derivative corresponding to the formula (I)

    F.sub.k H.sub.n Cl.sub.3-(k+n) C--CZ.sup.1 Z.sup.2 F       (I),

wherein Z¹ and Z² may be identical or different and represent hydrogen,fluorine, chlorine or bromine; k is 0, 1 or 2, and n is 2 or 3, saidmethod comprising reacting a halogenated alkene or halogenated alkanestarting compound with hydrogen fluoride in the presence of a catalystsystem in the liquid phase at a temperature between 0° and 250° C.,wherein hydrogen fluoride is present in said liquid phase in an at leastequimolar quantity relative to said starting compound; the molar ratioof starting compound to catalyst system is from about 10:1 to 1:100; thecatalyst system comprises a mixture of metal halide and a sulfonic acidderivative in a molar ratio of from about 100:1 to about 1:10; the metalhalide is selected from the group consisting of niobium pentahalide,tantalum pentahalide, molybdenum pentahalide and mixtures thereof; thesulfonic acid derivative is selected from the group consisting offluorosulfonic acid and perfluoro-lower alkane sulfonic acids with 1 to4 carbon atoms, and the starting compound is

a) a halogenated alkene corresponding to the formula (II)

    F.sub.k H.sub.m Cl.sub.2-(k+M) C═CX.sup.1 X.sup.2      (II),

wherein X¹ and X² may be identical or different and represent hydrogen,fluorine, chlorine or bromine, k has the meaning given above and m is 0,1 or 2; or

b) a halogenated alkane corresponding to the formula (III)

    F.sub.k H.sub.n Cl.sub.3-(k+n) C--CY.sup.1 Y.sup.2 Y.sup.3 (III),

wherein k and n have the above meanings; Y¹ and Y² may be identical ordifferent and represent hydrogen, fluorine, chlorine or bromine, and Y³represents chlorine or bromine.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The method according to the invention for preparing fluorine-containingethane derivatives of the general formula (I)

    F.sub.k H.sub.n Cl.sub.3-(k+n) C--CZ.sup.1 Z.sup.2 F       (I),

wherein Z¹ and Z² may be identical or different and represent hydrogen,fluorine, chlorine or bromine; k is 0, 1 or 2 and n is 1, 2 or 3,comprises reacting a halogenated alkene or halogenated alkane as thestarting compound with hydrogen fluoride in the presence of a catalystsystem in the liquid phase at a temperature between 0° and 250° C., withthe hydrogen fluoride being present in the liquid phase at least in anequimolar quantity, relative to the starting compound, the molar ratioof starting compound to catalyst system being between about 10:1 and1:100; the catalyst system comprising a mixture of metal halide and asulfonic acid derivative in a molar ratio of from about 100:1 to about1:10; the metal halide being selected from the group consisting ofniobium pentahalide, tantalum pentahalide, molybdenum pentahalide andmixtures thereof; the sulfonic acid derivative being selected from thegroup consisting of fluorosulfonic acid and perfluoro-lower alkanesulfonic acids having 1 to 4 carbon atoms, in particulartrifluoromethane sulfonic acid, and wherein

a) a compound corresponding to the formula (II)

    F.sub.k H.sub.m Cl.sub.2-(k+m) C═CX.sup.1 X.sup.2      (II),

wherein X¹ and X² may be identical or different and represent hydrogen,fluorine, chlorine or bromine, k is 0, 1 or 2, and m is 0, 1 or 2, isused as the halogenated alkene, or

b) a compound corresponding to the formula (III)

    F.sub.k H.sub.n Cl.sub.3-(k+n) C--CY.sup.1 Y.sup.2 Y.sup.3 (III),

wherein k and n have the above meanings, Y¹ and Y² may be identical ordifferent and represent hydrogen, fluorine, chlorine or bromine, and Y³represents chlorine or bromine, is used as the halogenated alkane.

Within the scope of the present invention, the total of k and n is 1, 2or 3, and the total of k and m is 0, 1 or 2. Preferably in the startingcompounds of Formulae II and III, k represents 0, and X¹, X², Y¹ and Y²represent fluorine, chlorine or bromine.

The method may be operated at pressures from about 1 to 100 bar(absolute) and at temperatures from about 0° to 250° C. The pressure andtemperature are selected so that the reaction takes place in the liquidphase.

The ethane derivatives obtained in the method according to the inventiondiffer from the starting compounds in that they carry at least one morefluorine atom. For each fluorine atom introduced into the substratemolecule in this manner, hydrogen fluoride preferably is used in aquantity which corresponds at least to the stoichiometrically requiredquantity. A larger excess of hydrogen fluoride, for instance up tofifteen times the stoichiometrically required quantity or more, may alsobe used for hydrogen fluoride (HF) addition and/or for halogen-fluorineexchange.

When preparing derivatives containing trifluoromethyl groups fromunsaturated compounds, good results are achieved even if the quantity ofhydrogen fluoride used corresponds to from one to ten times thestoichiometrically required quantity.

The quantity of hydrogen fluoride to be used may exceed this quantity,which is required for hydrogen fluoride addition and/or for thechlorine-fluorine exchange on the alkene or alkane. If metal halideswhich contain chloride or bromide are used as catalyst constituents, itis expected that these metal halides will be present in the reactionmixture in the form of metal pentahalides containing greater or lesseramounts of fluorine as a result of exchange of chlorine or bromine forfluorine. For instance, niobium pentachloride may be converted intocompounds of the type NbCl_(5-x) F_(x), niobium pentabromide may beconverted into compounds of the type NbBr_(5-x) F_(x), tantalumpentachloride into TaCl_(5-x) F_(x), and tantalum pentabromide intocompounds of the type TaBr_(5-x) F_(x), where x is a number from 0 to 5.The same applies to the corresponding molybdenum halides. If thereforein a preferred embodiment niobium pentachloride or tantalumpentachloride is used as the metal halide, these may possibly be presentin the reaction mixture in the form of partially fluorinated orfluorinated metal compounds.

The foregoing statement regarding the quantity of hydrogen fluoride tobe used should therefore read in full: "For each fluorine atomintroduced into the substrate molecule, hydrogen fluoride isadvantageously used in a quantity which corresponds at least to thestoichiometrically required quantity, and additionally as much hydrogenfluoride as is required for any halogenfluorine exchange of the metalhalide." The statements made hereinafter concerning the stoichiometry ofthe hydrogen fluoride to be used for the addition of hydrogen fluorideand/or the halogen-fluorine exchange in the alkene or alkane are also tobe understood correspondingly. For simplicity, these statements do notexpressly mention each time that additional hydrogen fluoride may benecessary for any halogen-fluorine exchange of the metal halide.

In order to determine what amount of hydrogen fluoride is additionallynecessary for this halogen-fluorine exchange, a person skilled in theart can react the metal halide to be used with hydrogen fluoride inadvance. The quantity of hydrogen fluoride consumed and/or the quantityof hydrogen halide formed makes it possible to calculate the quantity ofhydrogen fluoride needed in addition to that required for reacting thehalogenated hydrocarbon used.

The following procedure is particularly simple and advantageous: themetal halide, for instance molybdenum pentachloride or pentabromide,niobium pentachloride or pentabromide, or tantalum pentachloride orpentabromide, is placed in a fluorination reactor, and hydrogen fluorideis added until no more hydrogen chloride or hydrogen bromide isproduced. After the addition of the sulfonic acid derivative, thehalogenated hydrocarbon which is to be fluorinated and the hydrogenfluoride required for the fluorination thereof are introduced into thecatalyst mixture. In this case it is not necessary to supply additionalhydrogen fluoride for the fluorination of the metal chloride or bromide.

It is advantageous for preparing lower fluorinated compounds, forinstance CHCl₂ CCl₂ F from CHCl₂ CCl₃ or CCl₂ ═CCl₂, CH₂ ClCCl₂ F fromCH₂ ClCCl₃ or CHCl═CCl₂, or CH₃ CCl₂ F from CH₃ CCl₃ or CH₂ ═CCl₂, tooperate in the lower temperature range, for instance between 50° and150° C. The degree of reaction can be monitored analytically, forexample, by taking samples and analyzing them by gas chromatography.

In this case the high degree of reaction of the method according to theinvention is advantageous.

Some examples of fluorine-containing ethane derivatives which can beprepared using the method of the invention together with a listingstarting compounds which can be used and the stoichiometrically requiredquantity of hydrogen fluoride, are given in the following Table 1.

                  TABLE 1                                                         ______________________________________                                        CCl.sub.2 ═CCl.sub.2 + HF → CHCl.sub.2 CCl.sub.2 F                 CCl.sub.2 ═CCl.sub.2 + 3 HF → CHCl.sub.2 CF.sub.3                  CHCl.sub.2 CCl.sub.3 + 3 HF → CHCl.sub.2 CF.sub.3                      CHCl.sub.2 CCl.sub.2 F + 2 HF → CHCl.sub.2 CF.sub.3                    CHCl.sub.2 CClF.sub.2 + HF → CHCl.sub.2 CF.sub.3                       CHCl═CCl.sub.2 + 3 HF → CH.sub.2 ClCF.sub.3                        CH.sub.2 ClCCl.sub.3 + 3 HF → CH.sub.2 ClCF.sub.3                      CH.sub.2 ═CCl.sub.2 + 3 HF → CH.sub.3 CF.sub.3                     CH.sub.3 CCl.sub.3 + 3 HF → CH.sub.3 CF.sub.3                          CHF═CF.sub.2 + HF → CH.sub.2 FCF.sub.3                             ______________________________________                                    

The advantages of the method according to the invention are especiallyevident in the preparation of higher fluorinated products. In thepreparation of higher fluorinated products, such as the preparation ofCHCl₂ CF₃ from CHCl₂ CCl₃, CHCl₂ CCl₂ F, CHCl₂ CClF₂, CCl₂ ═CCl₂ ormixtures thereof; the preparation of CH₂ ClCF₃ from CH₂ ClCCl₃, CH₂ClCCl₂ F, CH₂ ClCClF₂, CHCl═CCl₂ or mixtures thereof; or the preparationof CH₃ CF₃ from CH₃ CCl₃, CH₃ CCl₂ F, CH₃ CClF₂, CH₂ ═CCl₂ or mixturesthereof, it is advantageous to operate in the higher temperature range,for instance from 70° to 220° C. and at from 10 to 50 bar. Again, thedegree of reaction can be monitored by analyzing samples taken from thereaction mixture.

The method of the invention is therefore particularly advantageous forpreparing higher fluorinated compounds, in particular trifluoromethylgroup-containing ethane derivatives corresponding to the formula F_(k)H_(n) Cl₃₋(k+n) C--CF₃ (Ia), in which k represents 0, 1 or 2 and nrepresents 1, 2 or 3.

This preferred embodiment of the method according to the invention ischaracterized in that for preparing a fluorine-containing ethanederivative corresponding to the formula (Ia)

    F.sub.k H.sub.n Cl.sub.3-(k+n) C--CF.sub.3                 (Ia),

wherein k represents 0, 1 or 2, and n represents 1, 2 or 3, at atemperature from 0° to 250° C. and a pressure of 1 to 100 bar (absolute)

a) a halogenated alkene corresponding to the formula (II)

    F.sub.k H.sub.m Cl.sub.2-(k+m) C═CX.sup.1 X.sup.2      (II),

wherein k and m have the meanings given above, X¹ and X² representfluorine, chlorine or bromine, is reacted with hydrogen fluoride, withthe hydrogen fluoride being present in the reaction mixture in an amountcorresponding to at least one-fold the quantity stoichiometricallyrequired for the hydrogen fluoride addition and for the halogen-fluorineexchange on the alkene, or

b) a halogenated alkane corresponding to the formula (III)

    F.sub.k H.sub.n Cl.sub.3-(k+n) C--CY.sup.1 Y.sup.2 Y.sup.3 (III),

wherein k and n have the above meanings; Y¹ and Y² are fluorine,chlorine or bromine, and Y³ is chlorine or bromine, is reacted withhydrogen fluoride, with the hydrogen fluoride in the reaction mixturebeing present in an amount corresponding to at least one-fold thequantity stoichiometrically required for the halogen-fluorine exchangeon the alkane.

The advantages of the method according to the invention becomeparticularly apparent when the corresponding halogenated alkenes areused as the starting compound. The degree of conversion when using thesecompounds, which are actually very inert, is very high. The formation ofpolymers and of compounds produced by adding halogen instead of hydrogenfluoride, which is observed with other methods, is not observed, or isobserved only to a negligible extent, in the method of the invention.

According to a preferred embodiment of the method of the invention,halogenated alkenes are used as the starting compounds. In a firstreaction step, hydrogen fluoride addition compounds form initially. Ifit is intended to prepare lower fluorinated compounds which havevaluable properties, for instance as solvents, these compounds areisolated from the reaction mixture. If it is intended to prepare higherfluorinated products, particularly ethane derivatives containingtrifluoromethyl groups, the initially produced compounds can be isolatedand fluorinated again. Advantageously, however, the hydrogen fluorideaddition compounds produced initially in the first reaction step are notisolated, but are reacted in situ with additional hydrogen fluoride toproduce the desired higher fluorinated products.

To prepare alkanes with a CF₃ -group, fluorosulfonic acid isadvantageously used as the sulfonic acid derivative.

Alkenes which are at least partially fluorinated also can be used asstarting material. Thus, according to another preferred embodiment ofthe present invention, CF₃ CH₂ F can be prepared by reactingtrifluoroethylene with hydrogen fluoride in the presence of the catalystsystem formed from the metal halide and sulfonic acid derivative.Surprisingly, polymerization of the alkene is not observed.

The method of the invention is outstandingly suitable for preparingCHCl₂ CF₃ (R123). This very particularly preferred embodiment of themethod of the invention is characterized in that for preparing CHCl₂ CF₃

a) CCl₂ ═CCl₂ is reacted with hydrogen fluoride, with the quantity ofhydrogen fluoride in the reaction mixture corresponding to at leastone-fold the quantity stoichiometrically required for the hydrogenfluoride addition and for the chlorine-fluorine exchange on the alkene,or

b) CHCl₂ CCl₃, CHCl₂ CFCl₂, CHCl₂ CF₂ Cl or a mixture thereof is reactedwith hydrogen fluoride, with the quantity of hydrogen fluoride in thereaction mixture corresponding to at least one-fold the quantitystoichiometrically required for the chlorine-fluorine exchange on thealkane.

The preparation of CHCl₂ CF₃ from CCl₂ ═CCl₂ according to variant a) isvery particularly preferred. The molar ratio of CCl₂ ═CCl₂ to hydrogenfluoride is preferably from 1:3 to 1:100.

As already noted above, the molar ratio of metal halide to sulfonic acidderivative in the method of the invention must be from about 100:1 to1:10. If the proportion of sulfonic acid derivative in the catalystmixture rises above this value, the selectivity decreases, particularlywith respect to the preparation of ethane derivatives containingtrifluoromethyl groups. If the proportion of sulfonic acid derivative inthe catalyst mixture drops below this value, the conversion to higherfluorinated products decreases to unacceptable levels.

Advantageously, the molar ratio of metal halide to sulfonic acidderivative lies in the range from 10:1 to 1:3, particularlyadvantageously from 2:1 to 1:2.

As stated above, the molar ratio of starting compound to catalystmixture is from 10:1 to 1:100. In this case the number of moles of thecatalyst mixture is calculated by adding the number of moles of metalhalide and the number of moles of sulfonic acid derivative. If forinstance 1 mole starting compound is reacted with hydrogen fluoride inthe presence of a mixture of 0.5 mole niobium pentahalide and 0.5 molefluorosulfonic acid, the molar ratio of starting compound to catalystmixture in this case is 1:1.

Preferably the molar ratio of starting compound to catalyst mixture isfrom 10:1 to 1:10, particularly preferably from 2:1 to 1:5.

Preferably fluorosulfonic acid or trifluoromethane sulfonic acid,particularly preferably fluorosulfonic acid, is used as the sulfonicacid derivative.

Preferably niobium pentahalide, tantalum pentahalide or a mixturethereof is used as the metal halide, wherein halide denotes fluoride,chloride or bromide. Particularly preferably, niobium pentachloride ortantalum pentachloride is used as the metal halide. Excellent resultshave been obtained using catalyst mixtures comprising niobiumpentachloride or tantalum pentachloride and fluorosulfonic acid.

A very particularly preferred embodiment of the method is characterizedin that for preparing CHCl₂ CF₃, the starting compound CCl₂ ═CCl₂ isreacted with at least one-fold the quantity of hydrogen fluoridestoichiometrically required for hydrogen fluoride addition and for thechlorine-fluorine exchange on the alkene, in the presence of a catalystmixture of niobium pentahalide, tantalum pentahalide or a mixturethereof and of fluorosulfonic acid.

In the method according to the invention, moisture has a disruptiveeffect. The reaction is therefore advantageously carried out underconditions which prevent a harmful amount of water from entering thereaction mixture. Substantially anhydrous hydrogen fluoride is used.Depending on the quantity of hydrogen fluoride used, it may berecommended to dry the commercially available hydrogen fluoride beforeuse. Furthermore, it is recommended to keep the apparatus used in as drya condition as possible. For this purpose, lines, reaction vessels,apparatus for working up and storing products may be rinsed with drygases, for instance with dry air or dry nitrogen gas.

The reaction may be carried out in a batch process or continuously. Thereaction mixture may be worked up by passing the reaction productsthrough a gas scrubber and subsequently fractionally distilling theproducts.

The apparatus used for performing the method should be resistant tohydrogen fluoride, metal halides and the respective sulfonic acidderivative used. Advantageously, components made of teflon and specialalloys such as "Hastelloy", a hydrogen fluoride-resistant nickel alloy,are used.

The present invention also relates to a catalyst mixture which can beused in the method according to the invention. The catalyst mixtureaccording to the invention comprises a mixture of metal halide and asulfonic acid derivative in a molar ratio of 100:1 to 1:10, with themetal halide being selected from the group consisting of niobiumpentahalide, tantalum pentahalide, molybdenum pentahalide and mixturesthereof, and the sulfonic acid derivative being selected from the groupconsisting of fluorosulfonic acid and perfluoro-lower alkane sulfonicacids containing 1 to 4 carbon atoms, in particular trifluoromethanesulfonic acid.

A person skilled in the art can prepare this catalyst mixture by simplymixing the constituents.

A preferred catalyst mixture according to the invention can be obtainedby mixing molybdenum pentahalide, tantalum pentahalide or niobiumpentahalide, in particular the chlorides or bromides, with a sulfonicacid derivative and hydrogen fluoride. The hydrogen fluoride isadvantageously added in such a quantity that no more hydrogen chlorideor hydrogen bromide is released.

A particularly preferred catalyst mixture comprises metal halide andsulfonic acid derivative in a molar ratio of approximately 10:1 to 1:3,in particular 2:1 to 1:2.

Very particularly preferred catalyst mixtures comprise a mixture ofniobium pentahalide, tantalum pentahalide or a mixture thereof as themetal halide and fluorosulfonic acid, trifluoromethane sulfonic acid ora mixture thereof as the sulfonic acid derivative.

Catalyst mixtures which comprise a mixture of niobium pentahalide ortantalum pentahalide and fluorosulfonic acid yield excellent results inthe method of the invention.

Especially preferred catalyst mixtures according to the invention can beobtained by mixing niobium pentachloride or tantalum pentachloride andfluorosulfonic acid and reacting this mixture with hydrogen fluorideuntil the release of hydrogen chloride has ended.

The invention further relates to hydrogen fluoride solutions for use inthe method according to the invention, which contain 0.01 to 99.99% byweight, preferably 10 to 90% by weight, and particularly preferably 30to 70% by weight, of the catalyst mixture according to the invention.These hydrogen fluoride solutions can be obtained by mixing the metalhalide and the sulfonic acid derivative in the required quantity ofhydrogen fluoride and optionally separating any hydrogen chloride orhydrogen bromide formed.

The fluorine-containing ethane derivatives produced by the method of theinvention are valuable, environmentally compatible solvents, propellantsand intermediate products for chemical synthesis.

The method according to the invention is distinguished by highconversion and high selectivity, and it can advantageously be performedin the liquid phase.

The high effectiveness of the method according to the invention must beviewed as surprising and unexpected. For instance, if perchloroethyleneis used as the starting compound and pure trifluoromethane sulfonic acidis used as the catalyst, the conversion is low, and partialpolymerization of the starting compound is observed. When usingfluorosulfonic acid as the catalyst, the yield is insignificantly small.Molybdenum pentachloride as the catalyst does give a very high degree ofconversion. However, the formation of higher fluorinated products suchas R123 takes place only to a very limited extent, and furthermore theexpensive catalyst becomes unusable after only a single performance ofthe experiment. Niobium pentachloride as a catalyst yields lower degreesof conversion. It was therefore completely unexpected that thecombination of these catalyst constituents, which individually arepractically unusable, in the method according to the invention shouldlead to such good results with respect to the degree of conversion,selectivity and life of the catalyst mixture and also permits thepreparation of higher fluorinated products, such as in particular R123.

The following examples are intended to explain the method according tothe invention in greater detail, without restricting its scope.

EXAMPLES

All the experiments were carried out in the same apparatus. The reactionwas carried out in a laboratory autoclave of V4A steel (a steel alloyedwith chromium, nickel and molybdenum). The internal volume of thisautoclave was 0.25 liters. The autoclave was equipped with a magneticstirrer, an immersion tube through which it was possible to meter in thestarting compounds, and a thermoadapter, by means of which it waspossible to measure the internal temperature. The laboratory autoclavealso had a gas outlet, which was connected to a gas scrubber filled withwater. The gas scrubber was in turn connected to a low-temperaturecondensation apparatus.

General method for performing the experiments for Examples 1 to 5

The metal halide, the sulfonic acid derivative and the halogenatedhydrocarbon used were introduced into the autoclave via the immersiontube with the aid of a metering pump. Then the hydrogen fluoride wasalso metered in via the immersion tube. Evolution of hydrogen chloridewas immediately observed, presumably resulting from the reaction of themetal chloride used and hydrogen fluoride. A hydrogen fluoride solutionwas formed which contained the catalyst mixture. The evolved hydrogenchloride was withdrawn from the laboratory autoclave and conveyed to thegas scrubber, where it was absorbed by the water present therein.

As soon as the evolution of hydrogen chloride which was initiallyobserved had ceased, the laboratory autoclave was closed, heated to themaximum temperature given in the examples, then brought to ambienttemperature, resulting hydrogen chloride gas was released, the autoclavewas closed and then heated again to the maximum temperature. Thisheating was effected by means of an oil bath. The maximum temperaturewas then maintained for 5 hours. Subsequently, the laboratory autoclavewas cooled to room temperature (approximately 22° C). The autoclavecontents were then brought to ambient pressure, and volatileconstituents were passed through the gas scrubber. Hydrogen chloride andhydrogen fluoride present were washed out in the gas scrubber. The crudegas leaving the gas scrubber and consisting substantially of organiccompounds was analyzed by gas chromatography. The crude gas leaving thegas scrubber was transferred into a low-temperature condensation unit.If desired, the crude product could be separated further by working upby distillation.

EXAMPLE 1 Preparation of trifluorodichloroethane anddifluorotrichloroethane

27 g niobium pentachloride (0.1 mole), 15 g trifluoromethane sulfonicacid (0.1 mole), 40 g tetrachloroethylene (0.24 mole) and 40 g hydrogenfluoride (2.0 mole) were introduced into the autoclave with the aid ofthe metering pump. Once the initially observed evolution of hydrogenchloride had ended, the autoclave was closed and heated to a maximumtemperature of 160° C. The pressure rose to 33 bar absolute. Aftercooling, the autoclave contents were worked up as described above.Analysis of the remaining, non-volatile reaction residues showed that100% of the tetrachloroethylene had been reacted.

The gas chromatography analysis of the gas phase yielded the followingvalues:

3.1% by weight C₂ HF₅ ; 0.6% by weight C₂ HClF₄ ; 50.2% by weight C₂HCl₂ F₃ ; 44.3% by weight C₂ HCl₃ F₂ ; 0.8% by weight C₂ Cl₄ F₂.

The example shows that with niobium pentachloride and trifluoromethanesulfonic acid as catalyst mixture, tetrachloroethylene can be convertedunder the given conditions into higher fluorinated ethanes, inparticular trifluorodichloroethane and difluorotrichloroethane.

EXAMPLE 2 Preparation of trifluorodichloroethane

27 g niobium pentachloride (0.1 mole), 10 g fluorosulfonic acid (0.1mole), 40 g tetrachloroethylene (0.24 mole) and 40 g hydrogen fluoride(2.0 mole) were introduced into the laboratory autoclave. After releaseof the initially evolved hydrogen chloride, the autoclave was closed andheated to a maximum temperature of 130° C., whereby the pressure rose to19 bar absolute. After cooling, the autoclave was brought to normalpressure, and volatile constituents were separated. Analysis of thenon-volatile residue showed that 99.9% of the tetrachloroethylene usedhad been reacted. The volatile constituents were passed through a gasscrubber, and the crude product leaving the gas scrubber was analyzedusing gas chromatography. The analysis yielded the followingproportions:

0.4% by weight C₂ HF₅ ; 0.1% by weight CHF₃ ; 0.8% by weight C₂ HCl₂ F₄; 81.2% by weight C₂ HCl₂ F₃ ; 16.7% by weight C₂ HCl₃ F₂.

This example shows that when niobium pentachloride and fluorosulfonicacid are used as the catalyst mixture, tetrachloroethylene is convertedinto trifluorodichloroethane in good yield and with good selectivity.

EXAMPLE 3 Preparation of trifluorodichloroethane fromdifluorotrichloroethane

5 g niobium pentachloride (0.02 mole), 14 g fluorosulfonic acid (0.14mole), 33 g difluorotrichloroethane (0.16 mole) and 40 g hydrogenfluoride (2.0 mole) were introduced into the laboratory autoclave. Theinitially evolved hydrogen chloride was again released. After thisinitial hydrogen chloride formation had abated, the laboratory autoclavewas closed and heated to a maximum temperature of 125° C. The pressurerose to 25 bar absolute. After cooling, the autoclave was brought tonormal pressure and volatile constituents were separated. The volatileconstituents were passed through the gas scrubber, and the crude productleaving the gas scrubber was analyzed using gas chromatography. Thefollowing values were obtained:

0.3% by weight C₂ H₂ Cl₂ F₂ ; 66.7% by weight C₂ HCl₂ F₃ ; 2.5% byweight C₂ Cl₃ F₃ ; 30.5% by weight C₂ HCl₃ F₂.

The conversion of difluorodichloroethane was found to be 49.1% byweight.

EXAMPLE 4 Preparation of trifluorodichloroethane anddifluorotrichloroethane from fluorotetrachloroethane

5 g niobium pentachloride (0.02 mole), 14 g fluorosulfonic acid (0.14mole), 36 g fluorotetrachloroethane (0.16 mole) and 40 g hydrogenfluoride (2.0 mole) were introduced into the autoclave. The initiallyevolved hydrogen chloride was released, and the autoclave was closed andheated to a maximum temperature of 130° C. The pressure rose to 22 barabsolute. The autoclave was cooled to room temperature and brought toambient pressure. The volatile constituents were passed through the gasscrubber, and the crude product was analyzed using gas chromatography.The following values were obtained:

1.7% by weight CHF₃ ; 2.9% by weight CHClF₂ ; 0.6% by weight C₂ H₂ Cl₂F₂ ; 46.4% by weight C₂ HCl₂ F₃ ; 0.8% by weight C₂ Cl₃ F₃ ; 47.6% byweight C₂ HCl₃ F₂. The degree of conversion was found to be 63.6% byweight. Examples 3 and 4 demonstrate the suitability of the method ofthe invention for preparing higher fluorinated haloalkanes fromcorrespondingly lower fluorinated haloalkanes.

EXAMPLE 5 Preparation of trifluorochloroethane from trichloroethylene

36 g tantalum pentachloride (0.1 mole), 10 g fluorosulfonic acid (0.1mole), 32 g trichloroethylene (0.24 mole) and 40 g hydrogen fluoride(2.0 mole) were introduced into the autoclave. The initially evolvedhydrogen chloride was released again. After the initial hydrogenchloride formation had abated, the autoclave was closed and heated to amaximum temperature of 140° C., with the pressure rising to 43 barabsolute. After cooling, the autoclave was brought to ambient pressure,and volatile constituents were passed through the gas scrubber. Thecrude product leaving the gas scrubber was analyzed by gaschromatography. The following values were obtained:

89.0% by weight C₂ H₂ ClF₃ ; 7.9% by weight CCl₃ F; 0.4% by weight C₂HCl₂ F₃ ; 0.4% by weight C₂ H₂ Cl₂ F₂ ; 2.3% by weight unknowns.

The conversion of trichloroethylene was 100% by weight.

EXAMPLE 6 Semi-continuous preparation of trifluorodichloroethane

In this example, the apparatus described above was used. 36 g tantalumpentachloride (0.1 mole), 10 g fluorosulfonic acid (0.1 mole), 40 ghydrogen fluoride (2 mole) and 40 g tetrachloroethylene (0.24 mole) wereintroduced into the autoclave before the first heating phase. Theinitially evolved hydrogen chloride was released. Then a hydrogenfluoride solution was again present which contained the catalystmixture. The autoclave was then closed and subjected to the firstheating phase. For this purpose, the autoclave contents were heated tothe temperature given in Table 2 and kept at this temperature during theperiod given in Table 2. Then the autoclave contents were brought toambient temperature, and the resulting hydrogen chloride was released.Then a sample of the compounds which were volatile at ambienttemperature and normal pressure was taken and analyzed by gaschromatography to determine the organic compounds contained therein. Theanalysis values, given in % by weight, are given in Table 2.

The autoclave contents were thereafter subjected to the second heatingphase. After cooling, the reactor was brought to normal pressure, andthis time the entire content of the compounds which were volatile atambient temperature and normal pressure was released from the reactorand passed through the gas scrubber. The crude product leaving the gasscrubber was analyzed by gas chromatography.

40 g tetrachloroethylene and 40 g hydrogen fluoride were then introducedagain into the reactor, in which the catalyst mixture had remained inaddition to the nonvolatile organic compounds. The reactor was thensubjected to the third heating phase, cooled, resulting hydrogenchloride was released, and then a sample of the organic compounds whichwere volatile at ambient temperature and normal pressure was analyzed.Thereupon, the reactor was subjected to the fourth heating phase,cooled, and the entire content of compounds which were volatile atambient temperature and normal pressure were passed from the reactorinto the gas scrubber, whereupon the crude product leaving the gasscrubber was again analyzed by gas chromatography.

In this manner, a total of 10 heating phases were carried out. After thefirst, third, fifth, seventh and eighth heating phases, only theresulting hydrogen chloride was released from the reactor, and sampleswere taken each time for analysis. Each time after the second, fourth,sixth and ninth heating phases, the total reactor content of compoundswhich were volatile at ambient temperature and normal pressure wasreleased from the reactor and passed through the gas scrubber, and thecrude product leaving the gas scrubber was analyzed.

Correspondingly, after the second, fourth, sixth and ninth heatingphases, 40 g hydrogen fluoride and 40 g tetrachloroethylene wereintroduced each time into the reactor. The catalyst mixture was neithersupplemented nor replenished or regenerated during the entireexperiment.

The maximum temperature attained in each heating phase, the maximumpressure reached, the time period over which the maximum temperature wasmaintained, and also the data obtained from the gas chromatographicanalysis of the gas phase after each heating phase are compiled in Table2.

                                      TABLE 2                                     __________________________________________________________________________        Max.                                                                              Max.                                                                  Heat.                                                                             Temp.                                                                             Press.                                                                            Time                                                                              C.sub.2 H.sub.2 Cl.sub.2 F.sub.2                                                    C.sub.2 H.sub.2 ClF.sub.3                                                           C.sub.2 HCl.sub.3 F.sub.2                                                           C.sub.2 HCl.sub.2 F.sub.3                   Phase                                                                             (°C.)                                                                      (bar)                                                                             (hour)                                                                            %     %     %     %                                           __________________________________________________________________________    1   120 39  3.0 0.1   0.2    3.6  94.7                                        2   130 14  5.0 --    0.2    2.3  97.0                                        3   120 35  5.0 --    --     6.1  92.7                                        4   120 17  6.0 0.1   0.1    4.0  95.2                                        5   120 34  7.5 0.2   0.1   14.4  84.2                                        6   120 27  7.0 0.1   0.1   21.1  82.4                                        7    90 10  4.0 --    --    10.0  88.9                                        8   105 11  6.0 --    --     8.3  90.9                                        9   110 11  6.0 --    --    18.1  81.2                                        10  110 11  7.0 3.5   --    16.5  79.8                                        __________________________________________________________________________     "%" means % by weight.                                                   

The resulting dichlorotrifluoroethane consisted of R123 and also tracesof R123a.

After completion of the tenth heating phase, the overall conversion oftetrachloroethylene was 91% by weight. In the organic part of thereaction residue (48 g) there was 0.8% by weighttrifluorodichloroethane, 37.6% by weight difluorotrichloroethane, 37.6%by weight tetrachloroethylene, and also 23.9% by weightfluorotetrachloroethane. This example demonstrates the suitability ofthe method of the invention for semi-continuous and continuousoperation. Due to the stability of the catalyst mixture, the proportionof higher fluorinated ethanes, particularly trifluorodichloroethane anddifluorotrichloroethane, is still very good even after a long reactiontime.

EXAMPLE 7 Preparation of 1,1,1,2-tetrafluoroethane (R134a) fromtrifluoroethylene and hydrogen fluoride

The apparatus used in this example corresponded in principle to theapparatus used in Examples 1 to 6. Since the trifluoroethylene startingcompound is gaseous at standard conditions, it wasn't introduced intothe autoclave by a metering pump. The immersion tube leading into theautoclave was connected via shut-off valves with a pressure gas cylindercontaining trifluoroethylene. By appropriately opening the valves,gaseous trifluoroethylene from this pressure cylinder could beintroduced into the autoclave.

Initially 39.8 g tantalum pentachloride (0.11 mole) and hydrogenfluoride were introduced into the autoclave and reacted to form tantalumpentafluoride quantitatively. Afterwards 23.6 g fluorosulfonic acid(HSO₃ F) (0.23 mole) were added.

Then 72 g hydrogen fluoride (3,6 mole) were added in liquid form, and 18g trifluoroethylene (0.22 mole) were forced into the autoclave. Theautoclave was closed and maintained for a period of two hours at 110° C.The overpressure was 15 to 17 atmospheres.

Gaseous reaction products then were passed through the gas scrubber anddirectly analyzed by gas chromatography combined with mass spectrometry(GC-MS analysis). It was found that 99.5% by weight of the gaseousreaction products consisted of tetrafluoroethane (R134a). The reactionproducts further contained 0.1% by weight water (entrained in the gasscrubber) and 0.4% by weight C₂ F₃ H₃ (equal amounts of R143 and R143a).The contents of the reactor were worked up hydrolytically. No polymericproducts of trifluoroethylene were found.

This example demonstrates that trifluoroethylene can be reacted withhydrogen fluoride according to the present invention to produce R134awithout formation of polymers. Even the crude product is so pure thatfor most uses, further purification would be superfluous.

EXAMPLE 8 Preparation of 1,1,1,2-tetrafluoroethane (R134a) fromtrifluoroethylene and hydrogen fluoride

The procedure corresponded to that described in Example 7. This time,however, the overpressure was only about 14 atmospheres, the reactiontemperature Was 103° C., and the reaction time was about 1 hour.

    ______________________________________                                        Starting material:                                                                         20.8 g (0.25 mole) trifluoroethylene                                          76 g (3.8 mole) hydrogen fluoride                                             catalyst (as in Example 7)                                       GC-MS Analysis:                                                                            2.1% water (entrained in the scrubber)                                        1.6% 143a                                                                     0.7% 143                                                                      95.6% R134a.                                                     ______________________________________                                    

Even with a shorter reaction time and milder reaction conditions, thepurity of the product is outstanding.

The foregoing description and examples have been set forth merely toillustrate the invention and are not intended to be limiting. Sincemodifications of the described embodiments incorporating the spirit andsubstance of the invention may occur to persons skilled in the art, thescope of the invention should be construed to include all variationsfalling within the ambit of the appended claims and equivalents thereof.

What is claimed is:
 1. A catalyst mixture comprising a mixture of metalhalide and a sulfonic acid derivative in a molar ratio of from 100:1 to1:10, wherein said metal halide is selected from the group consisting ofniobium pentahalide, tantalum pentahalide, molybdenum pentahalide andmixtures thereof, and the sulfonic acid derivative is selected from thegroup consisting of fluorosulfonic acid and perfluoro-lower alkanesulfonic acids with 1 to 4 carbon atoms.
 2. A catalyst mixture accordingto claim 1, wherein said sulfonic acid derivative is trifluoromethanesulfonic acid.
 3. A catalyst mixture according to claim 2 produced bymixing metal halide, sulfonic acid derivative and hydrogen fluoride. 4.A catalyst mixture according to claim 2 ,wherein the metal halide andthe sulfonic acid derivative are present in a molar ratio of from about10:1 to 1:3.
 5. A catalyst mixture according to claim 4, wherein saidmetal halide and said sulfonic acid derivative are present in a molarratio of from about 2:1 to 1:2.
 6. A catalyst mixture according to claim2, wherein said metal halide is selected from the group consisting ofniobium pentahalide, tantalum pentahalide and mixtures thereof, and saidsulfonic acid derivative is selected from the group consisting offluorosulfonic acid, trifluoromethane sulfonic acid, and mixturesthereof.
 7. A catalyst mixture according to claim 6, comprising amixture of niobium pentahalide or tantalum pentahalide andfluorosulfonic acid.
 8. A hydrogen fluoride solution for use inpreparing a fluorine-containing ethane derivative corresponding to theformula

    F.sub.k H.sub.n Cl.sub.3-(k+n) C--CZ.sup.1 Z.sup.2 F       (I)

wherein Z¹ and Z² may be identical or different and represent hydrogen,fluorine, chlorine or bromine; k is 0, 1 or 2, and n is 1, 2 or 3, saidsolution containing from about 0.01 to 99.99% by weight of a catalystmixture according to claim 16.